A couple of decades ago, the conventional wisdom was to put a UV filter on the end of every lens "to protect your investment." I used to do that. But Derrel is right, it takes a lot to damage a lens and a lens hood is very good protection. And I've seen a range of articles where people will stack 3-4 UV filters and shoot, then take the same shot without any filter and the difference (even on a computer) is distinct and obvious.
So now, I have a default wide-angle zoom I use for shooting outside and it has a circular polarizing filter on it (which I sometimes take off). I will put NDF and graduated NDFs on my lens when the situation calls for it. But otherwise, I shoot naked.